US2412552A - Heat exchanger - Google Patents

Description

Dec. 17, 1946.

D. c. AFFLECK HEAT EXCHANCER 2 Sheets-Sheet 1 INVENTORI Filed June 6, 1945 Patented Dec. 17, 1946 HEAT EXCHANGER David C. Aflleck, Hammond, Ind, assignor to Carnegle-Illinois Steel Corporation,

of New Jersey a corporation Application June 6, 1945, Serial No. 597,907

This invention relates generally to heat exchangers, and more particularly to an improved construction and arrangement of the bricks forming the checkerwork thereof.

While not limited thereto, the herein claimed invention has its greatest utility in the checkerwork used in hot blast stoves'of the type used for preheating air supplied to support combustion and bring about reducing reactions in a blast furnace.

As is known to those skilled in the art, such hot blast stoves are in the nature of a huge bricklined steel shell approximately 20 feet in diameter and 80 feet or more in height. Within the lining it is customary to provide a division wall defining the combustion chamber, and the balance of the space within the shell is filled with refractory brick checkerwork forming a system of upright fiues.

In normal operations, blast furnace gas is burned in the combustion chamber of the stove, and the hot burned gases passing through the multiplicity of fiues formed by the checkerwork gives up heat which is absorbed by the checkerbrick. At appropriate intervals the supply of combustion gas is cut d and the blast main is opened. Thus cold air under pressure is supplied to the stove. This air passes through the many fiues formed by the checkerwork and absorbs heat from the hot bricks and then fiows to the hot blast main leading to the bustle pipe of the blast furnace in a mannerwell known to those skilled in the art.

Practice has demonstrated that although blast furnace gas passes through primary washes before being introduced into the hot blast stove, there is still considerable dust entrained in the gas which has the tendency to precipitate on various ledges formed by conventional arrangements of checkerbrick. The checkerbrick heretofore used are open to various objections, the chief of which is that they are of such form that they promote the accumulation of objectionable dust deposits.

Many diiferent forms and shapes of refrac-.

tories have heretofore been devised for use as checkerbrick in hot blast stoves for preheating the air supplied to a blast furnace. In designing the shapes of checkerbrick to be used in order to promote the maximum eficiency, several factors must be kept in mind, such as stability, size of flue opening, brick volume, and heating surface. One of the most common types of checkerbrick used is a rectangular prismatic brick laid in horizontal layers commonly called basket weave, the brick being laid up in such a way that all vertical Joints are broken and a multiplicity of similar square flue openings extend from the bottom of the stove to the top thereof. such an arrangement is believed to structurally, be the best type of checkerwork known, but the ratio of volume of brick to heating surface is too high for maximum efiiciency. In a, properly designed hot blast stove there must be not only a suitable volume of brick to retain heat, but there must be adequate surface for moving gases or air to transmit heat either to or from the brick. The fiues formed by the conventional basket weave. checkerwork are solid walls without any by-paths from one flue to another. Thus any obstruction in the due such as a brickbat will render that flue useless for its entire length.

There is a known type of hot blast stove which employs brick of rectangular prismatic form with the upper corners cut oil and with a hole through the center of each brick. This known form makes a free opening between each flue and allows for cross movement of gas and air from one flue to another, decreasing the volume of brick in the regular checker chamber and exposing more surface. This known type'of checkerbrick is in the form of a rectangular prism, with upper opposite corners cut off on the diagonal. The surface exposed by the diagonal out, however, is only a theoretical heating surface, since the valley formed by the contact of two such checkerbrick in ashort time becomes filled with flue dust carried in suspension by the blast furnace gas. .When this valley becomes filled with dust the effective heating surface is materially reduced and of course will no longer be exposed to air and gas passage. The cross hole of this prior art brick provides for cross-flow of gas or air between flues, but it soon becomes filledwith flue dust and its intended function is thus defeated. The prior art brick referred Figure 4 is a similar sectional elevation on line IVIV of Figure 2.

Figure 5 is a detail perspective view of two adjacent perpendicularly disposed bricks forming part of the checkerwork shown in Figures 1 to 3 inclusive.

Figure 6 is an isometric view illustrating the three-point bearing which each individual checkerbrick makes with underlying bricks.

Figure "I is a perspective view illustrating a slightly modified form of checkerbrick.

Figure 8 is a perspective view of a checkerbrick somewhat similar to Figure 5, showing a further modification.

Figure 9 is an exploded isometric view illustrative of the method of assembling checkerbrick of the modified form shown in Figure 8, the view showing the relative positions of individual bricks and the arrows suggesting the operations necessary to lay up the checkerwork.

Referring particularly to the ence numeral ii] represents the shell of a conventional hot blast stove, and i2 the lining thereof. Spaced from the lining i2 is an arcuate wall is defining a conventional form of combustion chamber IS. The remainder of the structure is substantially filled with checkerwork, indicated generally at i8, the design and construction and arrangement of the particular checkerbricks making up this checkerwork constituting the herein claimed features ofthe invention. My

invention is an improvement over the above mentioned Seaver cross-vent checkerbrick. the

drawings, referare bounded by a horizontal bottom edge 88 and faces 30, and they converge to the point 32 and are bounded by triangular faces 34 which thus are obliquely so disposed as to prevent the accumulation of dust thereon.

The lower end faces 86 of all the bricks shown two vertical parallel end edges 40 and two converging end edges flwhich meet-at a common peak point as shown. The lower and faces 36 are all perpendicular to the bottom faces of the bricks. Thus said end faces in the assembled checkerwork are adapted to lie fiush against the lower portions of the side faces of bricks laid up perpendicular thereto, as clearly shown in Figures 3 to 6. As shown in Figures 4 and 6, it is apparent that the bricks are so shaped and proportioned that each one has a three-point bearing on three underlying bricks, one of said underlying bricks being perpendicular to each supported brick and the two other underlying bricks extending in the same direction as each supported brick.

Having thus described my invention, what I desire to secure by Letters Patent is outlined in the appended claims.

I claim:

l. A heat exchanger including checkerwork comprising a multiplicity of substantially identical bricks laid up in vertically spaced courses, each course including adjacent bricks perpendicular to each other and forming a multiplicity of flues, each brick having parallel top and botsaid Seaver checkerbrick consisting essentially of a rectangular prism with the upper corners bev-' eled off square and with a hole extending transversely through the brick.

In my improved checkerbrick the plane of the sloping surface is not perpendicular to the sides of the checker, but on the contrary, each sloping portion includes at least two oblique or warped planes, each sloping downwardly and outwardly, as viewed in plan.

As shown in Figures 1 to 6, the sloping planes of my improved brick may be flat oblique faces 20-20 with the dividing ridge line a-.b extending to about the top of the slope, as shown in Figure 5, or as shown in Figure 7, the two faces 20* -40 may be warped surfaces bounded by the curved side edge lines 0-11, the top edge line b'd, the diagonal straight ridge line a'-b', and the oblique end edge lines a-c.

As shown in Figures 1 to 6, the bricks constituting the checkerwork are laid up in basketweave pattern, by which I mean that any given horizontal course of bricks, as viewed in plan, comprises several parallel longitudinal rows 1-! and several parallel transverse rows t-t; thus the bricks of such longitudinal and transverse rows are perpendicular to one another as clearly suggested by relative positions thereof shown in the isometric views of Figures 5 and 6.

-- perpendicular prising a lower face in a plane perpendicular to A feature common to all embodiments 'of the I invention is that the oblique ends of the bricks are entirely devoid of horizontal surfaces on which dust can collect. The oblique edge planes, as shown, thus tend to shed dust. The triangular spaces 24 (best shown in Figures 3 and 4) between the bricks extending in one direction and those arranged perpendicular thereto provide for cross-flow between the several upright fiues 26 defined by the basket weave arrangement of checkerwork illustrated.

In the modification of Figures 8 and 9, the bevel end faces 28 are erpendicular to the s d tom horizontal rectangular faces and' parallel vertical side faces, each bottom face being mate rially greater in area that each top face, each end of each brick comprising a lower upright portion perpendicular to the bottom and a peaked top, portion and two oppositely inclined faces starting at said peaked top portion and extending toward the top face of the brick.

2. A checkerbrick of the character shown and described, having substantially parallel horizontal top and bottom rectangular faces, the bottom face being of materially greater area than the top face and having substantially parallel vertical side faces, the upright edges of the lower portion of each side face being parallel and the upper edge portions of each side face converging upwardly, each end of each brick having a lower portion perpendicular to the bottom face and a peaked top portion, and a pair of upwardly converging inclined oblique portions extending from said peaked portion to the top of the brick.

3. A checkerbrick of the character described, having top and bottom faces which are substan-. tially parallel, vertical side faces substantially thereto, each end of the brick comsaid bottom face and having a pointed upper portion whose converging upper edges intersect at a peak intermediate said top and bottom faces, and a pair of oppositely sloping end faces at each end of the brick extending upwardly from said converging upper edges.

4. A checkerbrick of the character described,

' having top and bottomfaces which are substantially para1le1,.vertica1 side faces substantially perpendicular thereto, each end of .the brick comprising a lower face having a pointed upper portion whose upper edges converge to a peak intermediate said top and bottom faces, and a pair of oppositely sloping endfaces at each end of the brick extending from said converging upper edges to the top face of the brick.

DAVID C. AFFIECK.

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